downside to going massive cams is that you tent to move the point where power actually kicks in up int he RPM range, trick is not to go too large on the cam profile otherwise they become ineffective before rpm point X..

eg in the rb26, i was considering 272 cams, but they only really egtw orking at about 5k rpm, so really you limiting your power band down a bit, where as 264's, bring in turb nice and early, and i have a really wide useable power band..

food for thought, bigger isn't always better...

as for going bigger displacement, porivded they can show the block will hold together <doubtful> you'e be better of going a rebuilt with forged slugs, good rods, balance and blueprint the crank, and looking at a cam profile that suits your turbo choice...

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Jesus Built my car, Its a love affair, Mainly Jesus and my hotrod